It is known that .alpha.,.alpha.'-bis(t-butylperoxy) diisopropylbenzene having the formula: ##STR1## may be used as a crosslinking agent for a variety of polymers including low and high density polyethylene, ethylenepropylene copolymer, ethylene-propylene terpolymer rubber, natural rubber, butadiene-styrene rubber, polybutadiene, polyisoprene, polychloroprene, sulfochlorinated polyethylene, chlorinated polyethylene, silicone rubbers, and blends of these polymers or blends with other polymers. This peroxide is particularly effective as a crosslinking agent for ethylene-propylene terpolymer rubbers and blends of ethylene-propylene terpolymer rubbers with silicone rubbers.
While .alpha.,.alpha.'-bis(t-butylperoxy) diisopropylbenzene is an effective crosslinking agent for the polymers listed above, the resulting crosslinked product may be subject to blooming. Blooming is the migration to the surface of the cross-linked product of white, normally crystalline materials which causes nonuniform coloration in crosslinked articles, particularly in those which are dark colored due to the presence of fillers, pigments or dyes.